A wireless mesh network employs two or more processing points (Mesh Points (MP's)) where neighboring MP's communicate with each other directly over the air via a wireless communication mechanism. A wireless mesh network can be a wireless Personal Area Network (PAN), wireless Local Area Network (LAN), or wireless Wide Area Network (WAN). Each MP in a wireless mesh network may have more than one neighboring MP that it can directly communicate with and it is free to choose any of these neighboring MP's as a next hop to forward its traffic as part of the best suitable path to a given destination.
A wireless mesh network can be implemented at Layer 2 (data link layer) or Layer 3 (Internet Protocol (IP) Layer) of the network protocol stack. 802.11 wireless technologies have been used for communication among MP's and also used for routing and path selecting operations, which occur at Layer 2 of the protocol stack. This type of wireless mesh network is referred to as a Layer-2 wireless mesh network. Moreover, this arrangement implies that the wireless mesh network can have out-of-order and duplicate end-to-end delivery of Layer 2 data frames.
In a multi-hop wireless mesh network, out-of-order and duplicate frames result from the normal dynamics of the wireless network, including but not limited to: changed routing decisions for wireless data frames traversing the network. Furthermore, the rate of changed routing decisions can become more severe as the rate of topology changes, load level variations occur, and/or wireless channel fluctuations increase. As a result, the probability of out-of-order and duplicate frames can increase significantly.
However, a wireless mesh network implemented at Layer 2 is expected to provide duplicate free and in-order delivery of data frames for the next-higher layer (Layer 3) of the protocol stack. Layer 3 typically depends upon duplicate free and in-order data delivery for its normal operation.